Thursday, February 5, 2009

Palstar AT2K

Palstar makes some of the best antenna tuners out there! Last year after much research I got their AT2K model. The build quality is simply amazing. This tuner almost tunes my standard G5RV on 160 meters. It also work on 6 meters due to the smaller roller inductor. The built-in Peak-reading watt/SWR cross-needle meter works really well and with very good accuracy.

Internal picture of AT2k. Most components are manufactured in-house by Palstar, including both variable capacitors and the roller inductor. The quality of the components is impressive - everything is very solid and heavy duty - indeed "built like a tank". All solder joints are perfect.

Roller inductor, 160m inductor (toroid) and switch-in relay. The high-power balun transformer (toroid) is visible at top-right.

Load and tune high-voltage variable capacitors - top-left is the power/SWR detector, top-right is the PCB of the peak-and-hold circuit. At bottom-left is visible the ceramic rotary RF switch.

Palstar AT2K and Heathkit SB-200 in my shack. AT2K looks stylish and it is very easy to operate! The two vernier dials allow for very fine tuning.

2010 Update: The current version of AT2K was changed from the original design. As a cost-saving measure, the internal 4:1 balun (used with balanced antennas) was removed from the tuner and it is now sold separately as an external option. Another change is in the inductor - the original inductor was 18 uH and was padded with extra 10 uH inductor for 160m only. The new inductor is 28 uH, eliminating the extra inductor, relay and switch at the expense of the tuning resolution.


N5UUA - Jon said...


I am waiting on one of these tuners to arrive. One of the things I noticed about this version as compared to what you shared is that the newer model lacks inability. The tuner will replace an MFJ-989D which has served me very well but I have traded it off to a friend. I am really looking forward to receiving the tuner and may provide further input to your blog once I get acquainted with it.

Jon - N5UUA

N5UUA - Jon said...

The AT2K arrived a few days ago, I am impressed with the build quality but I did run into a slight issue with the Inductor circuit when first trying to tune up on my 160M inverted-L antenna. The suggested settings in the manual were the opposite of what was needed for my antenna in particular. I was able to tune but when I tried to run the power up with my amp online something started arching over.

At first, I could not tell if it was in the amp or if it was in the AT2K. After pulling the covers on both and inspecting it was determined that it must be in the relay circuit (160m/80-6m circuit) that the arching took place. That told me that the tuner was experiencing too much inductive reactance and the solution was to run the roller inductor to minimum inductance with maximum capacitance coupling to start out with.

Using an antenna analyzer I was able to make adjustments that resulted in an acceptable match with mainly capacitance coupling and to minimize any reactance I did have to use a little of the roller inductor inductance to achieve a proper tune that would handle 1200 plus watts SSB.

As for the tuner operation and efficiency on all other bands... I love it from 160 to 6 meters! Palstar makes a great product.

Jon - N5UUA